The present disclosure relates to a light reflecting member, a light beam extension device with the light reflecting member incorporated therein, an optical device with the light beam extension device incorporated therein, and an image display device with the optical device incorporated therein.
A virtual image display device (an image display device) for making an observer observe a virtual image made by enlarging a two-dimensional image formed by an image forming device by a virtual image optical system is disclosed in, for example, Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2005-521099 or Japanese Unexamined Patent Application Publication No. 2006-162767.
As illustrated as a conceptual diagram in FIG. 40, an image display device 1000 includes an image forming device 1011 having a plurality of pixels arranged in the form of a two-dimensional matrix, a collimating optical system 1012 which turns light emitted from the pixels of the image forming device 1011 into collimated light, and a light guide unit 1030 in which light turned into the collimated light by the collimating optical system 1012 is incident thereon, is guided therein, and then emitted therefrom. The light guide unit 1030 includes a light guide plate 1031 in which incident light is propagated by total reflection in the inside and then emitted therefrom, a first deflection section 1040 (constituted by, for example, a single light reflecting film) which reflects light incident on the light guide plate 1031 such that the light incident on the light guide plate 1031 is totally reflected in the inside of the light guide plate 1031, and a second deflection section 1050 (constituted by, for example, a light reflecting multilayer film having a multilayer laminated structure) which emits light propagated by total reflection in the inside of the light guide plate 1031 from the light guide plate 1031. Then, if, for example, a HMD (Head Mounted Display) is constituted using the image display device 1000, a reduction in the weight and a reduction in the size of the device can be attained.
Alternatively, a virtual image display device (an image display device) using a hologram diffraction grating in order to make an observer observe a virtual image made by enlarging a two-dimensional image formed by an image forming device by a virtual image optical system is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2007-094175 or Japanese Unexamined Patent Application Publication No. 2007-012530.
As illustrated as conceptual diagrams in FIGS. 41 and 42, an image display device 1100 basically includes an image forming device 1111 displaying an image, a collimating optical system 1112, and a virtual image optical system (a light guide unit 1130) on which light displayed on the image forming device 1111 is incident and which guides the light to a pupil 41 of an observer. Here, the light guide unit 1130 includes a light guide plate 1131, and a first diffraction grating member 1140 and a second diffraction grating member 1150 each constituted by a reflection type volume hologram diffraction grating provided at the light guide plate 1131. Then, light emitted from each pixel of the image forming device 1111 is incident on the collimating optical system 1112, and collimated light is created by the collimating optical system 1112 and is incident on the light guide plate 1131. The collimated light is incident and emitted from a first surface 1132 of the light guide plate 1131. On the other hand, the first diffraction grating member 1140 and the second diffraction grating member 1150 are mounted on a second surface 1133 of the light guide plate 1131 which is parallel to the first surface 1132 of the light guide plate 1131.